This will be short cause I don't have much time right now. I just got this on an impulse buy on clearance (open box). At $160 I could not resist.

Sounds amazing via USB on Windows 8.1 with latest drivers. I don't have alot of higher end DACs to compare it to but I have had alot of aftermarket sound cards and decent portable Amp/DACs like the TEAC HA-P50. It's a huge step up from that, which was my previous daily DAC/Amp. Very neutral, bass is very well controlled.

The headphone amp is a good pair with all my headphones from 20-300ohm. The HD 600 needs no more than 11 o'clock on the dial. I thought my HD 600 was already great, now it sounds simply divine. My only gripe is the lack of volume control for the Line Out. Overall I am very pleased indeed, specially at this price. But I could see how some would pay $500-600 and never look back. I would if I wasn't so poor.

I had considered many of the comments made by fellow members regarding what to buy for under a grand that would improve my listening station - all replies were good and appreciated, The first issue was the need to replace a HeadRoom Total BitHead and a HeadRoom Supreme upgraded to reference amp some years ago. This is when the Teac UDH01-S Digital to Analog Converter with USB Audio Interface became my solution. It allows 3 digital inputs USB, coaxial, and optical with a selector button to chose the source and has balance and unbalanced outputs The headphone volume control with 1/4 jack is placed on the front panel as well as syncs on any signal from 44 to 192 with LEDs indicating it has locked on to the signal. The details of what is inside is listed below but I think of what does it sound like followed by what does it look like then can I afford it in that order. So I will say a very well known headphone amp/dac engineer said it should be sound very nice based on the details of what is inside the box for those who gobeyondThevenin'stheorem. What I didn't like is having to install software to make the USB work and that it had to be downloaded from a Japanese site rather than an including a disc sort of sucks. And as long as I am being picky a stepped volume control would have been a nice upgrade, but it isn't a big deal. So, why I like the Teac is it doesn't sound like most OP AMPs or tubes but it is close and it is always ready to play. The looks are nice despite a somewhat faux glass and metal but again how does it sound is why I bought it. Now if I wanted portability I clearly would have bought the HeadAmp offering for roughly the same money. I have Krell gear and have owned some of the best tube stuff but frankly it is the sound not the constantly farting with replacing tubes and re-biasing that I enjoy. I liked the idea of the Pass units but the listing on the sight turned out to be either no longer valid or they didn't bother to reply (very disappointing) . As a side bar because like many audio nuts I have often been caught on the wrong side of changing technology and thought newer must be better but really devoting time to listen without caring so much if this is the best possible is my solution.

7/15 Follow up - the TEAC unit developed some type of glitch allowing it to randomly flip back to the PC speakers despite the DAC lock still being illuminated. To resolve the problem you had to unplug and reinsert the usb cable. TEAC was less than responsive in helping - despite doing everything thing I could imagine including changing PCs and cables, I was forced to return the unit. Fortunately it was bought from Dedicated Audio so there weren't any issues in returning it.

I have replaced it with a demo PS Audio Digital Link III which has performed beautifully without the slightest issue. The software to connect via usb to the PC is internal and requires nothing on the user part. The build quality is much more solid than the Teac but I have been hard pressed to hear any sound improvement. There are still PS Audio units available for $500 (same price as the TEAC)

The UD-H01 is a dual digital/analogue converter containing two BurrBrown DAC chipsets (Type 1795) and a Tenor USB Audio Class 2 Interface. Thanks to the high-quality nature of these components, digital audio data from an external PC is converted to an analogue signal in high resolution Hi-Fi quality using up to 32 bit, 192 kHz asynchronous conversion technology. The resulting analogue signal can be sent to either a set of active loudspeakers or to an external amplifier. The UD-H01 is supplied with both balanced and unbalanced audio output connectors and a headphone connector complete with separate volume control. Two audio inputs (digital RCA and optical) allow connecting additional sources i.e. CD or DVD player.